Spherical Pt-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a spherical Pt-based catalyst as well as a preparation method and application thereof. According to the pore size distribution of the spherical Pt-based catalyst, the pore volume of pores with the pore size smaller than 2 nm accounts for 0.9%-4.0% of the total pore volume, and the pore volume of pores with the pore size ranging from 2 nm to 50 nm accounts for 95.0%-99.1% of the total pore volume. The catalyst is used for propane dehydrogenation reaction, and has high propane conversion rate and propylene selectivity and good stability.

Description

Technical Field

[0001] The present invention relates to a spherical Pt-based catalyst, a preparation method thereof and an application thereof, in particular to a spherical Pt-based catalyst suitable for a fluidized bed, a preparation method thereof and an application thereof. Background Art

[0002] The shape and size of catalyst particles are generally determined according to the requirements of the reactors used in industrial production. At present, there are four common types of reactors in industry: fixed bed, fluidized bed (boiling bed), suspension bed and moving bed. Fixed bed reactors commonly use spherical, cylindrical bar, clover, four-leaf and flake catalysts. Moving bed reactors often use large particle spherical catalysts. Fluidized bed reactors generally use spherical or bar catalysts with smaller particles.

[0003] Spherical catalysts have good fluidity and a high packing coefficient, with uniform fluid distribution, low resistance and small pressure drop, etc., and are widely used in the technology of dehydrogenating light alkanes to produce olefins.

[0004] At present, the catalysts for dehydrogenating light alkanes to produce olefins are mainly prepared by loading active component Pt and other additives on a γ-Al 2 O 3 support, such as EP100222A, CN1185994A, etc. However, since the dehydrogenation reaction is carried out at a high temperature of about 600 °C, the high reaction temperature often causes a large amount of carbon deposition on the catalyst. As the use time of the catalyst increases, the catalyst needs to be subjected to multiple high-temperature carbon burning regeneration treatments, resulting in the γ-Al 2 O 3 support being easily sintered and undergoing α-phase transformation, greatly reducing the specific surface area of the support and destroying the pore structure. Furthermore, the active components of the catalyst aggregate, and the activity of the catalyst drops severely. Therefore, it is necessary to further modify the γ-Al 2 O 3 support to make the catalyst have high thermal stability.

[0005] CN112973771A discloses a spherical catalyst support containing molecular sieve and alumina, its preparation and application. This catalyst support is obtained by precipitating an inorganic aluminum salt with ammonia water and acidifying to obtain a sol, adding a mixed solution of ball-milled pseudo-boehmite and molecular sieve and a sol modification additive to the sol, then dropping and forming in an oil-ammonia column for aging, and finally washing, drying and calcining to obtain a composite small ball with high strength and large specific surface area. This method is to mix the suspension slurry obtained by ball-milling pseudo-boehmite and molecular sieve with a dilute sol and then peptize again, which will have the disadvantage of uneven dispersion of the molecular sieve. At the same time, the doping of solid molecular sieve will also lead to a decrease in the strength of the support.

[0006] CN105478100A discloses a method for preparing silicon-containing γ-Al 2 O 3 spherical particles. The method is to stir and slurry pseudoboehmite dry gel powder and deionized water, add dilute nitric acid for acidification, then add urea and a predetermined amount of sodium silicate solution, stir for 5 hours, add kerosene and fatty alcohol polyoxyethylene ether and stir for 5 hours, drop and form spheres in an oil-ammonia column, cure the wet spheres in ammonia water for 2 hours, then filter, wash with deionized water, dry, and calcine to obtain silicon-containing γ-Al 2 O 3 spherical particles. The method for preparing γ-Al 2 O 3 spherical particles has a long curing time, difficult washing, and low production efficiency.

[0007] CN104289220A discloses a preparation method and use of a high thermal stability dehydrogenation catalyst for low-carbon alkanes. The method for preparing the carrier is to add an aluminum source to an alkaline aqueous solution, stir, continue to add the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, add a silicon source, stir, filter, age for 10-48 hours, drop and form spheres, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles containing Si element; or add an aluminum source to an alkaline aqueous solution, stir, continue to add the alkaline aqueous solution to adjust the pH of the mixed solution to 7-14, filter, wash with deionized water, then add dilute nitric acid to form a sol, stir, filter, age for 10-48 hours, drop and form spheres, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles, and then immerse the γ-Al 2 O 3 spherical particles in an aqueous solution or ethanol solution of a silicon source at 60-120 °C for 2-6 hours, and then dry and calcine to obtain γ-Al 2 O 3 spherical particles containing Si element. The disadvantages of this method are long preparation cycle, complex process, need to adjust the pH value, and cannot ensure product consistency. SUMMARY OF THE INVENTION

[0008] Aiming at the deficiencies of the prior art, the present invention provides a spherical Pt-based catalyst, a preparation method and an application thereof. The spherical Pt-based catalyst has the characteristics of good roundness, high crushing strength, large pore volume and pore diameter, uniform Pt loading, environmental protection and no peculiar smell of the product, and is used for propane dehydrogenation reaction, having high propane conversion rate, high propylene selectivity and good stability.

[0009] In the first aspect of the present invention, a spherical Pt-based catalyst is provided, wherein the pore size distribution of the catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.9% to 4.0% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 95.0% to 99.1% of the total pore volume, preferably 96.0% to 98.0%.

[0010] Further, the specific surface area of the catalyst is 70 - 116 m 2 / g, and the pore volume is 0.60 - 0.75 mL / g.

[0011] Further, the average diameter of the catalyst particles is 1.6 - 1.8 mm.

[0012] Further, the average pore diameter of the catalyst is 14 - 17 nm.

[0013] Further, the crushing strength of the catalyst is 72 - 81 N / grain.

[0014] Further, the true roundness of the catalyst is 95.6% - 99.9%.

[0015] Further, in the catalyst, based on the mass of the catalyst, by mass fraction, the content of Pt is 0.2% - 1.0%, the content of Sn is 0.09% - 0.9%, and the content of alumina is 98.1% - 99.8%.

[0016] In the second aspect of the present invention, a preparation method of the above spherical Pt-based catalyst is provided, including:

[0017] Mixing aluminum hydroxide sol with an aqueous Pt solution, dropping the obtained mixture into an oil-ammonia-oil-water four-layer mixing column for shaping, drying, and calcining to obtain a spherical Pt-based catalyst; in the oil-ammonia-oil-water four-layer mixing column, four layers are sequentially arranged from top to bottom, the first layer is the first oil layer, the second layer is the ammonia water layer, the third layer is the second oil layer, and the fourth layer is a tin-containing water layer.

[0018] Further, the tin-containing water layer includes a tin salt and hydrochloric acid, wherein the tin salt is at least one of stannous chloride or tin tetrachloride, preferably stannous chloride. Further, in the tin-containing water layer, the concentration of the tin salt is 0.5 wt% - 1.1 wt%, preferably 0.6 wt% - 0.8 wt%, and the concentration of hydrochloric acid is 5 wt% - 8 wt%.

[0019] Further, the alumina content in the aluminum hydroxide sol is 15 wt% - 26 wt%.

[0020] Further, the preparation method of the aluminum hydroxide sol includes: mixing aluminum hydroxide and water to make a slurry, adding a peptizing agent, and obtaining the aluminum hydroxide sol after stirring evenly. Further, the peptizing agent is selected from one or more of inorganic acids (such as nitric acid), organic acids (such as acetic acid, citric acid), and is preferably nitric acid. When the peptizing agent contains an inorganic acid, the mass concentration of the inorganic acid is 30% - 50%. When the peptizing agent contains an organic acid, the mass concentration of the organic acid is 30% - 50%. Further, the addition amount of the peptizing agent in terms of acid is 1wt% - 10wt% of the mass of aluminum hydroxide in terms of aluminum oxide, and is preferably 2wt% - 8wt%. Further, the aluminum hydroxide is preferably hydrated aluminum hydroxide, such as wet aluminum hydroxide material. Preferably, in the aluminum hydroxide, the water content is 17wt% - 25wt%. Preferably, the properties of the aluminum hydroxide after calcination are as follows: the specific surface area is 110 - 201m 2 / g, the pore volume is 0.8 - 2.0 mL / g, and the average pore diameter is 15 - 17 nm. The calcination conditions are as follows: the temperature is 600 - 850 °C, the time is 2 - 12 h, and the oxygen-containing atmosphere is such as air. The aluminum hydroxide can be commercially purchased or prepared by conventional methods. The aluminum hydroxide is preferably macroporous pseudo-boehmite containing water, and the water content is 19wt% - 23wt%.

[0021] Further, the platinum-containing compound in the Pt-containing aqueous solution is one or more of platinum chloride (PtCl 4 ), chloroplatinic acid (H 2 PtCl 6 ), and is preferably chloroplatinic acid. The concentration of the platinum-containing compound in the Pt-containing aqueous solution is 2wt% - 6wt%. The addition amount of the Pt-containing aqueous solution is 8% - 40% of the mass of the aluminum hydroxide sol in terms of aluminum oxide, and is preferably 15% - 30%.

[0022] Further, the oil-ammonia-oil-water four-layer mixing column is a straight column, preferably a cylinder.

[0023] Further, in the oil-ammonia-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil or diesel oil, and is preferably white oil. The kinematic viscosity of the white oil at 40 °C is 20 - 40 mm 2 / s, and is preferably 25 - 35 mm 2 / s. The height of the first layer is 30% - 50% of the height of the second layer.

[0024] Further, in the oil-ammonia-oil-water four-layer mixing column, the second layer is the ammonia water layer, and the concentration of the ammonia water is 20wt% - 28wt%, and is preferably 22wt% - 26wt%.

[0025] Further, in the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid seal oil layer, which is one or more vegetable oils with a density between the second ammonia water layer and the fourth tin-containing water layer and a kinematic viscosity at 40 °C of 60 mm 2 / s or less, preferably a mixed oil of castor oil and soybean oil. Among them, the volume ratio of castor oil to soybean oil is preferably 1 / 4 to 1 / 6. The kinematic viscosity of the castor oil at 40 °C is 500-650 mm 2 / s, preferably 570-600 mm 2 / s; the kinematic viscosity of the soybean oil at 40 °C is 10-25 mm 2 / s, preferably 13-17 mm 2 / s. The height of the third layer is 30%-50% of the height of the second layer, preferably 35%-45%.

[0026] Further, in the oil-ammonia water-oil-water four-layer mixing column, the fourth layer is the tin-containing water layer, which is prepared by dissolving a tin salt in hydrochloric acid. The height of the fourth layer is 1.0-2.0 times the height of the second layer, preferably 1.2-1.5 times. During the preparation of the spherical Pt-based catalyst, when the concentration of the tin salt is less than 0.5 wt%, a tin salt is added by an external circulating pump to make the concentration meet the above requirements.

[0027] Further, the preparation method of the oil-ammonia water-oil-water four-layer mixing column includes:

[0028] (1) Pour the materials required for the fourth layer into a columnar container (preferably a plexiglass container) and ensure the solution is uniform;

[0029] (2) Slowly add the materials required for the third layer on top of the fourth layer materials in step (1) and stabilize for 20-35 min;

[0030] (3) Slowly add the materials required for the second layer on top of the third layer materials in step (2);

[0031] (4) Slowly add the materials required for the first layer on top of the second layer materials in step (3) to obtain an oil-ammonia water-oil-water four-layer mixing column. Preferably, during the addition of the materials required for the first layer, a peristaltic pump is used to slowly circulate up and down above the interface between the first layer and the second layer, so as to weaken the surface tension at the interface between the first layer and the second layer. Then, it is left to stand for 30-60 min until it is stable. This can ensure that the aluminum hydroxide sol can quickly pass through the contact interface between the first layer and the second layer, prevent pauses from causing trailing, and affect the true roundness.

[0032] Furthermore, the shaping of the spherical Pt-based catalyst is carried out in an oil-ammonia water-oil-water four-layer mixing column. A mixture of aluminum hydroxide sol and an aqueous solution containing Pt is dropped into the oil-ammonia water-oil-water four-layer mixing column, wherein the inner diameter of the dropper used is 1.0 mm to 1.6 mm.

[0033] Furthermore, the residence time of the mixture of aluminum hydroxide sol and the aqueous solution containing Pt in the oil-ammonia water-oil-water four-layer mixing column is 5 - 18 s, preferably 7 - 11 s.

[0034] Furthermore, the drying temperature is 100°C to 150°C, and the drying time is 6 - 10 hours; the calcination temperature is 750°C to 950°C, and the calcination time is 1 - 4 hours.

[0035] The third aspect of the present invention provides the application of the above catalyst in the propane dehydrogenation reaction.

[0036] Furthermore, the application includes: propane raw material is contacted with the catalyst for dehydrogenation reaction to obtain the product propylene.

[0037] Furthermore, before the propane dehydrogenation catalyst is used, it needs to be reduced. The catalyst precursor is reduced under a reducing atmosphere. The reducing atmosphere is preferably H 2 , the reduction temperature is 450 - 600°C, and the reduction time is 1 - 3 h.

[0038] Furthermore, the propane dehydrogenation reaction conditions are preferably as follows: the reaction temperature is 500 - 600°C, the reaction pressure is 0 - 1 MPa, and the volume space velocity is 50 - 200 h -1 .

[0039] Compared with the prior art, the advantages of the present invention are as follows:

[0040] (1) The present invention synthesizes the spherical Pt-based catalyst by a one-step method. An aqueous solution containing Pt is added to the aluminum hydroxide sol, so that metallic Pt is uniformly dispersed in alumina, and at the same time, it also plays a role in pore expansion. The four-layer oil-ammonia water-oil-water mixing column is different from the two-layer oil-ammonia column or the hot oil column. The third layer of oil layer is added as a liquid seal oil layer and the fourth layer of tin-containing water layer, which can enable the sol to quickly enter the third layer and the fourth layer of tin-containing water layer after passing through the second layer of ammonia water layer, and the pH value is quickly reduced to neutral, so that the small balls are not easily broken or shrunk with the volatilization of the surface ammonia water during the drying process, resulting in a significant increase in the catalyst particle size and mechanical strength. At the same time, it enables full contact between the metal and the carrier and more uniform loading. Moreover, tin elements are introduced into the fourth layer of water column. Since the surface potential of the spherical sol is negative, Sn can be quickly adsorbed when passing through the tin-containing water column. 2+Ions introduce metal elements in one step during the synthesis of the support. By subsequent calcination, Sn-doped spherical alumina is obtained. This method is not only simple to operate, but also since adsorption mainly occurs on the outer surface, it will not block the pores. Moreover, during the solidification process, the interaction between Sn and alumina is enhanced, which is beneficial to improving the stability and dispersion after loading noble metals, and thus improving the catalyst activity. During the preparation process, the rapid decrease in the pH value on the surface of the sol spheres simultaneously causes a rapid decrease in the hydrophobicity of the colloidal particle surface, a significant increase in the interaction force between the colloidal particles, a shortening of the distance between the colloidal particles, and partial collapse of the original structure, resulting in an increase in the mesoporous structure within the range of 2 - 50 nm of the support. By adjusting the hydrochloric acid concentration in the fourth tin-containing water layer, the proportion of mesopores can be adjusted.

[0041] (2) The preparation process of the present invention is environmentally friendly. In the traditional oil-ammonia column spheroidization process, the volatilization of ammonia water brings serious environmental pollution problems and subsequent pollutant emission problems. In the present invention, the second oil layer separates the second ammonia water layer and the fourth tin-containing water layer, so that the ammonia water layer is sealed above the fourth water layer, which can extend the service time and avoid environmental pollution caused by the product carrying out ammonia water. After long-term use, the tin-containing water layer can be replaced to ensure the liquid sealing effect, which is simple to operate industrially and saves costs.

[0042] (3) The spherical Pt-based catalyst obtained by the preparation method of the present invention is used in the propane dehydrogenation to propylene reaction, and has a high propane conversion rate and propylene selectivity. The catalyst with large pore diameter and large pore volume can avoid carbon deposition after long-term operation, and has good stability and good reaction performance. Specific embodiments

[0043] The following further illustrates the spherical Pt-based catalyst, its preparation method and application effect in the present invention through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0044] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0045] In the present invention, the nitrogen adsorption and desorption curves of the samples are tested at -196 °C using the ASAP2020 full-automatic physical adsorption instrument of Micromeritics Company in the United States to measure the specific surface area, pore volume and pore size distribution.

[0046] In the present invention, the crushing strength is tested using the ZQJ-Ⅲ intelligent particle strength tester manufactured by Dalian Zhiqu Testing Machine Factory, and the average value of crushing ten spherical catalysts is measured.

[0047] In the present invention, the true roundness is measured by an electron microscope of Olympus Corporation, and the average value is calculated after testing 20 samples.

[0048] Example 1

[0049] Take 250 g of macroporous pseudo-boehmite filter cake with a moisture content of 22 wt% (calcined at 600 °C for 3 h in an air atmosphere, with the following properties: pore volume 0.87 ml / g, specific surface area 175 m 2 / g, average pore diameter 16 nm), add deionized water and stir to make a uniform slurry, then add 26 g of nitric acid solution with a mass concentration of 45% for peptization to finally prepare a pseudo-boehmite sol with an alumina mass content of 20%; take 300 g of the above sol (alumina content 20 wt%), add 12 g of chloroplatinic acid solution with a chloroplatinic acid concentration of 3%, stir evenly to obtain a sol mixture;

[0050] Use a dropper with an inner diameter of 1.2 mm to drop the above sol mixture into a four-layer mixing column (cylindrical) of (white oil with a kinematic viscosity of 32 mm 2 / s at 40 °C - ammonia water with a concentration of 25 wt% - mixed oil - stannous chloride aqueous solution) for shaping, and the residence time in the four-layer mixing column is 8 s. Among them, the addition amount of white oil is 35% of the volume of ammonia water, the addition amount of mixed oil is 38% of the volume of ammonia water, and the addition amount of stannous chloride aqueous layer is 1.3 times the volume of ammonia water; the mixed oil is composed of castor oil with a kinematic viscosity of 580 mm 2 / s at 40 °C and soybean oil with a kinematic viscosity of 15 mm 2 / s, and the volume ratio of the two is 1:5. The concentration of stannous chloride in the stannous chloride aqueous solution is 0.7 wt%, and the concentration of hydrochloric acid is 6 wt%. In the preparation process of the spherical alumina support containing tin, when the concentration of stannous chloride is less than 0.5 wt%, the concentration of stannous chloride in the stannous chloride aqueous solution is made the initial concentration by an external circulating pump. Then dry at 130 °C for 8 hours and calcine at 800 °C for 3 hours to obtain the spherical Pt-based catalyst A of the present invention. The physicochemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0051] Example 2

[0052] Compared with Example 1, the difference is that the hydrochloric acid concentration in the fourth layer of the four-layer mixing column is changed to 8 wt%, and the stannous chloride concentration of the tin salt is changed to 0.8 wt% to obtain the spherical Pt-based catalyst B of the present invention. The physicochemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0053] Example 3

[0054] Compared with Example 1, the difference is that the concentration of chloroplatinic acid used is changed to 6% to obtain the spherical Pt-based catalyst C of the present invention. The physicochemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0055] Example 4

[0056] Compared with Example 1, the differences are as follows: the white oil in the four-layer mixing column is changed to white oil with a kinematic viscosity of 23 mm 2 / s at 40 °C, at the same time, the ammonia water concentration is changed to 21 wt%, and the volume ratio of castor oil to soybean oil added is changed to 1:4, obtaining the spherical Pt-based catalyst D of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0057] Example 5

[0058] Compared with Example 1, the differences are as follows: the white oil in the four-layer mixing column is changed to a mixture of diesel oil and white oil with a mixing mass ratio of 1:1, at the same time, the ammonia water concentration is changed to 28 wt%, obtaining the spherical Pt-based catalyst E of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0059] Example 6

[0060] Compared with Example 1, the differences are as follows: the concentration of chloroplatinic acid is changed to 6%, the white oil is changed to white oil with a kinematic viscosity of 28 mm 2 / s at 40 °C, the ammonia water concentration is changed to 23 wt%, and at the same time, the volume ratio of castor oil to soybean oil is changed to 1:4, obtaining the spherical Pt-based catalyst F of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 1, and the composition is shown in Table 3.

[0061] Example 7

[0062] Compared with Example 1, the differences are as follows: the addition amount of white oil is 42% of the volume of ammonia water, the addition amount of the mixed oil is 32% of the volume of ammonia water, and the addition amount of the tin-containing water layer is 1.6 times the volume of ammonia water, obtaining the spherical Pt-based catalyst G of the present invention, and its analysis results are shown in Table 1.

[0063] Comparative Example 1

[0064] The synthesis step of the sol mixture is the same as that in Example 1.

[0065] Compared with Example 1, the differences are as follows: the four-layer oil-ammonia water-oil-water mixing column is changed to a two-layer oil-ammonia column, the upper layer is white oil with a kinematic viscosity of 32 mm 2 / s at 40 °C, the lower layer is ammonia water with a concentration of 25 wt%, the addition amount of white oil is 25% of the volume of ammonia water, and the remaining forming steps remain unchanged. After calcination, 100 g of the carrier is taken and saturatedly impregnated into an aqueous solution containing 0.4 g of stannous chloride. After impregnation for 30 min, it is dried in a drying oven at 90 °C for 10 h and calcined in a muffle furnace at 600 °C for 4 h, obtaining the comparative spherical Pt-based catalyst H of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 2, and the composition is shown in Table 4.

[0066] Comparative Example 2

[0067] The synthesis method of the sol mixture is the same as that in Example 1.

[0068] Compared with Example 1, the difference lies in that only the first layer of white oil column in the four-layer oil-ammonia water-oil-water mixing column is removed, and spherical granulation is carried out with a three-layer column to obtain the comparative spherical Pt-based catalyst I of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 2, and the composition is shown in Table 4.

[0069] Comparative Example 3

[0070] The synthesis method of the sol mixture is the same as that in Example 1.

[0071] Compared with Example 1, the difference lies in that only the fourth layer of tin-containing water column is removed. After roasting, 100 g of the carrier is taken and saturatedly impregnated into an aqueous solution containing 0.4 g of stannic chloride. After impregnation for 30 min, it is dried in a drying oven at 90 °C for 10 h and roasted in a muffle furnace at 600 °C for 4 h to obtain the comparative spherical Pt-based catalyst J of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 2, and the composition is shown in Table 4.

[0072] Comparative Example 4

[0073] The synthesis method of the sol mixture is the same as that in Example 1.

[0074] Compared with Example 1, the difference lies in that only the third layer of the mixed layer of castor oil and soybean oil in the four-layer oil-ammonia water-oil-water mixing column is removed to obtain the comparative spherical Pt-based catalyst K of the present invention. The physical and chemical properties of the obtained catalyst are shown in Table 2, and the composition is shown in Table 4.

[0075] Comparative Example 5

[0076] The synthesis method of the sol mixture is the same as that in Example 1.

[0077] Compared with Example 1, the difference lies in that the addition amount of white oil is 16% of the volume of ammonia water, the addition amount of the mixed oil is 20% of the volume of ammonia water, and the addition amount of the tin-containing water layer is 0.4 times the volume of ammonia water to obtain the comparative spherical Pt-based catalyst L of the present invention, and the analysis results are shown in Table 1.

[0078] Table 1 Physical and chemical properties of the spherical Pt-based catalysts obtained in each example

[0079] Catalyst Number A B C D E F G Average Particle Diameter, mm 1.79 1.76 1.77 1.79 1.73 1.76 1.74 <![CDATA[Specific surface area, m 2 / g]]> 95 92 96 97 97 98 98 Pore Volume, mL / g 0.671 0.675 0.670 0.661 0.660 0.670 0.658 Pore Size Distribution, % <2nm 2.6 2.5 2.6 2.9 2.7 2.6 2.6 2 - 50nm 97.1 97.3 97.2 97.0 97.1 97.3 97.3 >50nm 0.3 0.2 0.2 0.1 0.2 0.1 0.1 Average Pore Size, nm 16.4 16.7 16.2 15.4 15.2 16.3 15.3 Crushing Strength, N / particle 79 78 76 76 75 74 75 Roundness, % 97.2 97.3 97.2 96.9 96.7 96.8 96.8

[0080] Table 2 Physical and chemical properties of the spherical Pt-based catalysts obtained in each comparative example

[0081] Catalyst Number H I J K L Average Particle Diameter, mm 1.72 1.60 1.71 1.62 1.61 <![CDATA[Specific surface area, m 2 / g]]> 108 120 99 105 99 Pore Volume, mL / g 0.460 0.490 0.494 0.509 0.586 Pore Size Distribution, % <2nm 6.3 6.4 7.2 6.4 6.2 2 - 50nm 93.5 93.4 92.7 93.6 93.6 >50nm 0.2 0.2 0.1 - 0.2 Average Pore Size, nm 14.3 14.6 12.0 11.3 13.5 Crushing Strength, N / particle 52 39 38 46 49 Roundness, % 94.4 93.7 94.6 92.5 94.5

[0082] Table 3 Composition of the catalysts in each example

[0083] Catalyst Number A B C D E F G Aluminum Oxide (wt%) 99.5 99.4 99.3 99.5 99.5 99.3 99.5 Pt (wt%) 0.3 0.3 0.5 0.3 0.3 0.5 0.3 Sn (wt%) 0.2 0.3 0.2 0.2 0.2 0.2 0.2

[0084] Table 4 Composition of Catalysts in Each Comparative Example

[0085] Catalyst Number H I J K L Aluminum Oxide (wt%) 99.5 99.5 99.6 99.6 99.6 Pt (wt%) 0.3 0.3 0.2 0.3 0.3 Sn (wt%) 0.2 0.2 0.2 0.1 0.1

[0086] Catalyst Evaluation

[0087] Take 5 g of each of the above catalysts, first reduce them at 520 °C for 1.5 h in a hydrogen atmosphere, and then load them into a fixed-bed reactor respectively for the propane dehydrogenation activity evaluation: the reaction temperature is 550 °C, at atmospheric pressure, and the volume space velocity is 150 h -1 . The results of propane dehydrogenation are listed in Tables 5 - 8.

[0088] Table 5 Evaluation Results of Catalysts in Each Example for Propane Dehydrogenation

[0089] Catalyst Number A B C D E F G Propane Conversion after 1h Reaction, % 36.5 36.4 36.2 35.2 35.4 36.3 34.7 Propylene Selectivity after 1h Reaction, % 90.1 89.6 89.5 88.5 88.0 89.4 88.3

[0090] Table 6 Evaluation Results of Catalysts in Each Comparative Example for Propane Dehydrogenation

[0091] Catalyst Number H I J K L Propane Conversion after 1h Reaction, % 33.1 33.3 30.4 33.4 33.0 Propylene Selectivity after 1h Reaction, % 87.2 86.2 84.3 86.7 85.2

[0092] Table 7 Evaluation Results of Catalysts in Each Example for Propane Dehydrogenation Stability

[0093] Catalyst Number A B C D E F G Propane Conversion after 5h Reaction, % 30.2 29.9 29.4 28.1 28.2 29.2 28.0 Propylene Selectivity after 5h Reaction, % 80.2 79.5 79.6 75.9 76.4 77.7 75.2

[0094] Table 8 Evaluation Results of Catalysts in Each Comparative Example for Propane Dehydrogenation Stability

[0095] Catalyst Number H I J K L Propane Conversion after 5h Reaction, % 20.1 19.6 22.4 24.7 23.6 Propylene Selectivity after 5h Reaction, % 68.4 69.7 70.1 68.5 69.2

[0096] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A spherical Pt-based catalyst, wherein the pore size distribution of the catalyst is as follows: the pore volume of pores with a pore size less than 2 nm accounts for 0.9% to 4.0% of the total pore volume, and the pore volume of pores with a pore size of 2 - 50 nm accounts for 95.0% to 99.1% of the total pore volume, preferably 96% to 98%.

2. The catalyst according to claim 1, characterized in that: The specific surface area of the catalyst is 70 to 116 m 2 / g, and the pore volume is 0.60 to 0.75 mL / g; and / or, the average diameter of the catalyst is 1.6 - 1.8 mm; and / or, the average pore size of the catalyst is 14 - 17 nm; and / or, the crushing strength of the catalyst is 72 - 81 N / grain; and / or, the roundness of the catalyst is 95.6% - 99.9%.

3. The catalyst according to claim 1, characterized in that: in the catalyst, based on the mass of the catalyst and in terms of mass fraction, the content of Pt is 0.2% - 1.0%, the content of Sn is 0.09% - 0.9%, and the content of alumina is 98.1% - 99.8%.

4. The preparation method of the catalyst according to any one of claims 1 - 3, comprising: mixing aluminum hydroxide sol with an aqueous Pt solution, dropping the resulting mixture into an oil - ammonia - oil - water four - layer mixing column for shaping, drying, and calcining to obtain a spherical Pt - based catalyst; in the oil - ammonia - oil - water four - layer mixing column, four layers are arranged in sequence from top to bottom, the first layer is the first oil layer, the second layer is the ammonia layer, the third layer is the second oil layer, and the fourth layer is the tin - containing water layer.

5. The preparation method according to claim 4, characterized in that: the platinum - containing compound in the aqueous Pt solution is one or more of platinum chloride and chloroplatinic acid, preferably chloroplatinic acid; and / or, the concentration of the platinum - containing compound in the aqueous Pt solution is 2 wt% - 6 wt%; and / or, the addition amount of the aqueous Pt solution is 8% - 40% of the mass of aluminum hydroxide sol calculated as alumina, preferably 15% - 30%.

6. The preparation method according to claim 4, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the first layer is the first oil layer, which is selected from one or more of white oil and diesel oil, preferably white oil; the kinematic viscosity of the white oil at 40 °C is 20 to 40 mm 2 / s, preferably 25 to 35 mm 2 / s.

7. The preparation method according to claim 4, characterized in that: in the oil - ammonia - oil - water four - layer mixing column, the second layer is the ammonia layer, and the ammonia concentration is 20 wt% - 28 wt%, preferably 22 wt% - 26 wt%.

8. The preparation method according to claim 4, characterized in that: In the oil-ammonia water-oil-water four-layer mixing column, the third layer is the second oil layer, i.e., the liquid seal oil layer, which is one or more vegetable oils with a density between the second ammonia water layer and the fourth water layer and a kinematic viscosity of 60 mm 2 / s or less at 40°C, preferably a mixed oil of castor oil and soybean oil. Among them, the volume ratio of castor oil to soybean oil is preferably 1 / 4 to 1 / 6; And / or, the kinematic viscosity of the castor oil at 40 °C is 500 to 650 mm 2 / s, preferably 570 to 600 mm 2 / s; the kinematic viscosity of the soybean oil at 40 °C is 10 to 25 mm 2 / s, preferably 13 to 17 mm 2 / s.

9. The preparation method according to claim 4, characterized in that: in the oil - ammonia - oil - water four - layer mixing column, the tin - containing water layer comprises a tin salt and hydrochloric acid, wherein the tin salt is at least one of stannous chloride and tin tetrachloride, preferably stannous chloride; and / or, in the tin - containing water layer, the concentration of the tin salt is 0.5 wt% - 1.1 wt%, preferably 0.6 wt% - 0.8 wt%, and the concentration of hydrochloric acid is 5 wt% - 8 wt%.

10. The preparation method according to claim 4, characterized in that: the height of the first layer is 30% - 50% of the height of the second layer; and / or, the height of the third layer is 30% - 50% of the height of the second layer, preferably 35% - 45%; And / or, the height of the fourth layer is 1.0 to 2.0 times, preferably 1.2 to 1.5 times, the height of the second layer.

11. Use of the catalyst according to any one of claims 1-3 in the propane dehydrogenation reaction.

12. The use according to claim 11, wherein: Before use, the catalyst needs to be reduced; preferably, the reducing atmosphere is preferably H 2 , the reduction temperature is 450-600 °C, and the reduction time is 1-3 h.

13. The use according to claim 11, wherein: The reaction conditions are as follows: the reaction temperature is 500 - 600 °C, the reaction pressure is 0 - 1 MPa, the space velocity is 0.5 - 5 h -1 , and the hydrogen-hydrocarbon molar ratio is 0.5 - 3.0.